Control device



Aug- 24 1943 J. D. Bou-:SKY 2,327,336

CONTROL DEVICES Filed April 5; i939 s sheets-sheet 1 Aug. 24, 1943. J, D. BoLEs-KY 2,327,336

CONTROL DEVICES Filevd April 5, 1939 l 6 Sheets-Sheet 2 S u l 'gggmilllihll E@ (15. *iV/f Aug. 24, 1943. J. D. BoLEsKY- CONTROL DEVICES Filed April s, 193s 4 6 Sheets-Sheet 3 J. D. BOLESKY CONTROL DEVICES Filed April 5, 1939 6 Shee'lZS-Shee'rI 4 Aug. 24, 1943. J. D. BoLEsKY CONTROL DEVICES Filed April 5. 1939 6 Sheets-Sheet 5 Aug. 24, 1943. J. D. BoLEsKY CONTROL, DEVICES Filed April 5, 1939 6 Sheets-Sheet 6 Mgr ` Patented Aug. 24, 1943i.: l

CONTROL'DEVICE -John D. ABolesky, ttleboro, Mass., assignor to Metals & Controls Corporation,

- Mass.,

a corporation of Massachusetts Attleboro,

Application April 5,1939, serialize. 266,078 v 4o claims. (orfano-1313) This invention relates to control devices. and, with regard to certain more specific features, to electric snap switches and valves,. forexample, of both thermally and manually actuated types.

`Among the several objects of the invention may be noted the provision of a control device of the class described, which is capable of automatic operation to one controlling condition, butwhich is incapable of automatic operation to a second controlling condition, requiring manual actuation therefor; the provision of a control device, such as an electric switch, which can be used both to connect and disconnect a motor or other electrical device in whose circuit Ait is connected; mally responsive switch of the class described which in case of excess currents being drawn by the motor (or other electrical device) will automatically breakthe circuitr connections to the device; the provision of a thermally responsive control device of the class described which requires manual resetting in order againv to actuate the device; the provision of an electric switch of'the class described which is so constructed as to include novel means for preventing the formation of contact-destroying arcs; and the provision of control devices of the class described which are relatively economical to make, and safe in operation. Other objects will be in part obvious and in part pointed out here- .navften The invention accordingly comprises the ele-l nents and combinations of elements, features if construction, and arrangements of parts which will be exemplified in the structures herenafter described, and the scope of the applicazion of which will be indicated in the following claims.4

In the accompanying drawings, llustrated several of nents of the invention,

Fig. 1 is an isometric view of a thermostatic klectric switch of simple form embodying the resent invention;

Figures 2 and 3 are vertical cross sections aken substantially along lines 2-2 and 3 3 of ig. 1;

Fig. 4 is an isometric view similar to Fig. 1, lustrating another operating position of the ig. l switch; Fig. 5 is another isometric view similar to Fig.

in which are illustrating a third operating position of theig. 1 switch;

Figures 6 and 7 arev cross sections similar to ig. 3, illustrating alternative4 contact construcons;

Fig. 8 is a cross section similar to Fig 2, illus- 'ating an alternative form of mounting;

Fig. 9 is a cross section similar to Figures 3,

the provision of a thervarious 'possible embodi- Y 6 and 7, illustrating an alternative construction for the operating end of the thermostatic switch;

Fig. 10 is an isometric viewof a second form of switch embodying the. present invention;

Fig. 11 is a vertical cross section taken'sub-y stantially along line Il-II of Fig. 10;

Figures .'12 Vand 13 are isometric views similar to Fig. l0, iilustrating alternative positions of the switch of Fig'. 10

Fig. 14 is a top plan view of a third' form of switch embodying the present invention;

Fig. 15 is a vertical cross section taken substantially along line l5-l5 of Figi 14;

Figures 16, 17 and 18 are cross sections taken substantially along lines lli-IG, I8-l8, respectively of Fig. 15;

Fig. 19 is a view similar to Fig. 17, illustrating an alternative operating'positionof the Fig. 14 switch;

Fig. 20 is a. vertical cross section taken substantially along line 2li-2U of Fig. 19;

Figures 21, 22, 23 and 24 are electrical circuit diagrams showing certain uses of switches made in accordance with the present invention;

Fig. 25 is a cross section similar to Fig. 17, illustrating a Afourth switch embodiment of the invention;

Fig. 26 is a top plan view of a thermostatic element, used in the Fig. 25 embodiment;

Fig. 27 is a cross section taken substantially along line 21-`21 of Fig. 26:

Fig. 28 is a cross section similar to Fig. 16, illustrating a fifth switch embodiment of the present invention;

Fig. 29 is a cross section similar to Fig, 28, showing the switch thereof Iin an alternative position;

Fig. 30 is an axial cross section of a sixth, valve embodiment of the present invention;

Fig. 31 is'an axial section similar to Fig. 15 illustrating a seventh, non-thermostatic switch embodiment 'of the invention; and

Fig. 32 is a cross section similar to Fig. 17

illustrating an eighth, flasher switchy embodi,

ment of the invention.

Similar reference characters indicate corresponding parts throughoutthe several views of the drawings. y

While the present invention comprehends control devices of all sorts, its principal embodiment comprises an electric switch actuatable thermally and particularly adapted for motor protection usages. Other embodiments will also be described hereinafter. Electric switches of the type mentioned are used to make and break electrical circuits on the exceeding of certain safeelectrical currentl values in the motor power circuit.

4 Switches o1' this type are sometimes called Thermal cutouts and more particularly when applied to electric' motors, motor overload protective delT-l'l and y present invention tends to curl upwardly on decrease of temperature.

It will be appreciated that the only forces tending to hold the blade 6 in its Fig. 1 position are the deterri-ng forces between the faces of contacts l and 8. As soon, however, as this deterring force 1s reduced below the force of the tension of the switch, which is made of an electrical insulating v material, such as Bakelite, porcelain, or the like. Mounted as by a rivet-typeconstruction on the base I is a post 2 (see also Fig. 2) thetop surface of which is fiat except for a tapped hole 3. Fitting in the tapped hole 3 is a machine screw spring I0, as occasioned by the thermostatic blade 5 commencing to curl upwardly under change of ambient temperature, the tension of the spring l is relieved by rotating the blade 6 on the post 2, to the position shown in Fig. 4. It will be seen that this movement is in the nature of a rotation 4, which has, just beneath its head, an unthreaded portion of somewhat greater diameter than the threaded shank of the scr'ew. The screw .4 provides means for mounting a thermo-* static metal blade .or strip 6, one end of which has a hole 6a through which the portion 5 passes in a rotatable joint. The portion 5 is of sum- -cient axial length (preferably just slightly greater Athan the thickness of the thermostatic metal blade 6), so that when the screwv 4 is threaded down tightly into the post 2, Vit does not bind thethermost'atic blade 6 against pivoting movement, in its own plane, on the post 2.

The thermostatic blade 6 may be made of any suitable thermostatic material, such as the customary bimetal.

Mounted on the under side of the oppositeorl free end of the thermostatic metal blade -6 is an electrical contactbutton 1 the active face of which is presented downwardly. Mounted in poy sition on the base I to engage the contact button l is a relatively stationary, cooperating contact button .8. f

Numeral 9 indicates a post mounted on the base I, .which post 9 receives one end of a tension or coil spring I0. The other end of the coil -spring I0 is hooked tl'iroughl a small hol II orotherwiseattached to the edge of the thermostatic metal blade 6.'

- The various mountings are so arranged that;

when the ambientv temperature is at its proper value, the thermostatic blade '6 holds the contacts I 1 and 8.lrmly juxtaposed, in the manner indicated in'Fig. l.; Under such conditions, the spring I0 is in tension, tending to rotate the blade. on the post 2 in such/a manner as to disengage,

of the thermostatic blade in its own plane. Electrical connections between thecontacts 'l and 8 are thereby broken, and it will be noted that the break takes place, notvmerely through the relatively short distance represented by the thermoy static movement of the blade 6 but through a much greater distance' represented bythe rotative or angular displacement of contact l from contact 8.

When, now, the ambient temperature reverses' its trend, and returns tothe predetermined normal value, the thermostatic bladey 6 will tend to flatten', but unless external auxiliary actuation is employed, it will not in so flattening bring the contacts 'I and 8 back into juxtaposition, because of their angular displacement from 'each other through the action of the spring I0. The switch then assumes the position shown in Fig. 5,

for example.

It will be understood, of course, that in practical switch constructions suitable provisions are made for making -electrical connections to the contacts 1 and 8. In the interest of simplicity,

fsuch connections have been omitted from the showing of the present embodiment.

From the above, it will be seen that, with a minimum number of simple elements, a highly yeffective the'rmos'tatic electric switch has been provided, which switch operates automatically to open or interrupt its circuit in response to cer'- tain abnormal Atemperature conditions, but which will not automatically reestablish the circuit upon correction of the abnormal temperature conditions. In order to close the switch, the blade B must be manually or otherwise non-automatically rotated from. its Fig. 5 position back to its Fig. 1 position, and it will then vretain the Fig. 1` position only in the event that normal ambient tembya rotative movement, the contacts l and 8. However, the frictional pressure .between the contacts 1 and 8, engendered by the temperature-determined force'i-n the bimetallic blade 6, i

is, at the desired normal ambient temperature,

. sufficient to overcome the tension of the Spring I0, and the switch as a whole is therefore stable in its position represented by Fig. 1v when the.

ambient temperature is at a given level.

The thermostatic blade 6 is so mounted that upon change oftemperature in a desired direction away from the established predetermined carrying the contact l. For example, if it is desired to break connections on rise of ambient temperature, the-thermostatic metal blade Bis so arranged that its free end curls upwardly on rise v of temperature. In the alternative, if it is de-` sired to break electrical connections on decrease of temperature below a predetermined level, the thermostatic metal blade 6 'is so disposed that it perature lconditions have been reestablished, sc

that suicient friction is brought about between the'contacts 1 and 8vto oppose the tension oi spring I0. H

It is to be noted that the switch described i: capable of manualopening at any time, prio] to automatic opening thereof.v All that needs'tx 4be done in order to manually open the switcl is. to lift the contact 'l from the .contact 8, t4

-reduce the pressure therebetween, and thereupol vthe spring I0 pulls the blade 6 to its Fig. 5 posiI temperature, it tends to curl upwardly at its end An exceedingly simple switch capable of auto matic. or manual opening, but capable only o manual reclosing, is thereby provided.

Y Figures 6 and 7 illustrate alternative embodi ments for the structure of the cooperating face of contacts I and VIl, the purpose 'being to in crease the interfacial friction. In Fig. 6, fo example, the contact 'I has a convexoperatin face I2, while. the contact 8 has a concave oper ating face I3.into which the convex face I2 c the contact 'I fits. It is evident that-with given amount of thermostatic pressure holdin blade 6. AIn the base I fitted in the bushing I is a post the contacts 1 and II together, a substantial force will be required to wipe the contact 1 away from the contact 8. Similarly, in-Fig. 7, the contacts:l

y screw I9 tightly clamps the thermostatic metal blade 6 to the head I1 of post I6, so that the piv x oting of. the blade 6 now takes place by rotating the post I6 in the collar or bushing I5. The post I6, it will now be seen, rotates coextensively with the operative rotations of the thermo'- static metal blade 6, and this rotative movement may be used to control whatever type ofdevice it is desired to operate. electric switch`is desired, the'rotatable post I6 may mount and control the action of a mercury Or, if'

switch or some similar` switching means.

it is desired to controla. valve, such as a stop `cock valve,` the post I6 may be connected to directly rotate the cock of the valve.

I5. Rotatably For example, if. an s 3 Following the principles heretofore enunciated.

the -thermostatic disc' 23, when at a predetermined normal temperature, holds the respective con- I tacts 25and 26 juxtaposed with sumcient pres- When the construction of Fig. 8 is used, and A the control is effected by the rotatable post I6,

it is no longer necessary (although it may be desirablel' that electrical contacts 1 and 8 be provided as in the previous embodiments. Alternatively, aV construction Fig. 9 may be provided. Here it will' be seen that the end of the blade 6 is provided y with, lfor example, an insulating material rivet having a convex face 2I engaging a suitable concave depression` 22 formed directly in the base I. In such anembodiment, the deterring force opposing the rotative tendency of the thermostatic metal blade 6 under the tension of the spring I 0 is brought about by the engagement of convex face 2| of the rivet 20 with the concave depression 22 in the base I. The action, however, is largely the same as in the previously described embodiment.

Figures 10, ll. more complicated y has been replaced by a snap-acting thermostatic disc shown in John- A. Spencer Patent 1,448,240, for example. As shown in Fig. 1l, the disc 23 is mounted on the post 2 by the screw 4 in a manner similar to the Fig. 2 embodiment, the disc 23 being provided with a central hole 24 for receiving the oollargportion 5 of the screw 4. The mounting thus afforded isl suiciently loose that such as illustrated in 23, of the type i nections from the Fig.

sure so that their interfacial friction isl great enough to oppose the tendency of the tension spring to rotate the disc 23 on post 2.' However, as soon as the ambienttemperature changes through a suiicient extent, the disc 23, due to its inherentcharacteristics, will snap to a position of opposite concavity, as illustrated in Fig. 12,'and

"in so doing it releases the pressure betweenrespective contacts 25 and 26-and eliminates the interfacial friction therebetween, so that the spring I0 at once rotates the disc 23 on the post 2 until said spring I0 has`assumed a straight line position connecting posts 9 and'2. In this manner, both the contacts 25 are not only lifted away from stationary contacts 2B, but are also angularly displaced or wiped away therefrom. On subsequent change of ambient temperature in the reverse direction, the disc 23 snaps back to its original direction of concavity, but it .does so at its new angular position on the post 2, and the contacts `25 and 26 are therefore not re-juxtaposed. Unthe switch assumes the posid er such conditions, tion shown in Fig. 13. To reestablish circuit con- 13 position, the disc 23 must be manually rotated back to its Fig. l0 position.

It will accordingly be seen that the embodiment of Figures 10 through 13 operates in accordance with the same principles as the embodiment of Fig. 1. It should be understood. of course, that the variations represented by Figures 6, 7, 8 and 9 may likewise be utilized in the embodiment of Fig. 10.

Furthermore, it is to be noted that it is not necessary that the concave -thermostatic disc 23 be of a snap-acting type. On the contrary, a concave thermostatic disc that moves slowly, or creepsVbetween its positions of opposite concavity y may be used with success. as the rapidity with the disc can undergo the desired rotative movementwithout binding.

To the under, normally concave surface of disc 23 are anixed, at diametrically opposite points, a

pair of relatively movable electric 25. In cooperating positionv on mounted a pair of cooperating stationary contact buttons 26.

In this embodiment the tension spring Ill is so positioned that, when the contacts 25 and 2B are respectively juxtaposed, it component on the edge of disc 23, tending to cause said disc to rotate or pivot on the post 2.

contact buttons pulls with a tangential the base I are Vself automatically;

and distance through which spring III angularly displaces disc 23 once theinterfacial contact pressure decreases below a given amount, is suicient to eliminate any arcing problem on separation of the contacts.

Figures 14 through 20 show a practical switch embodiment of the invention following the general principles of the embodiment of Fig. 10. The embodiment of Figures 14 through 20 have been particularly designed for use as a thermal cutout, -or "motor overload protective device. This switch automatically breaks circuit connections when the current value exceeds a predetermined limit, or when the ambient temperature exceeds a predetermined limit. This switch willnot re-set itthat is to say, once circuit connections have been broken', manual actuation is needed in order to reestablish such circuit connections. This isI a valuable protective feature in connection with motor overload protection. The switch is so constructed, however, that it may be manually disconnected orconnected'at any time: and it is accordingly useful as a starting and stopping switch for the motor.

Referring toFigures 14 through 20, numeral 30 indicatesa base for the l struction, comprising a bottom portion 3I and an upstanding, generally cylindrical wall 32. Pro- -jecting out of the top of the cupshaped base is has the very practical feature that it switch of cup-like conof which will be given in h lite, porcelain, etc.

head for adjusting purposes.

'.through, say, about 60 of arc.

ably hexagonal collar or Vnut 55,

greater detail hereinafter. Beth the base an and the knob 33 are preferably made of an electrical insulating material, such 'as molded Bake- Base 3U is preferably pr'ovided with external mounting ears 29.

Mounted centrally in the bottom 3| of the base 30 is a threaded post 34, which has a polygonal A lock nut36 secures the relative adjustment of the post 34 in the bottom 3|. On the other side ofV the bottom 3|, thepost 34 is extended into knob 33 as an unthreaded cylindrical portion 31 of reduced diameter..' A

Extending through the bottom 3 l of the base 30 are three Ielectrical terminal pieces 38, 39 and 40, the angular disposition of 34 is indicated in Fig. 18. Terminalpieces 38 and 39,` it will be seen, are diametrically opposite each other. The angular position of terminal piece is relatively immaterial.

The terminal pieces 38, 39 and 40' comprise sheet metal stampings whichare force-fitted intol the bottom 3| of base 30, affording" internal contact faces 4|, 42 and 43, respectively, and external loops 44, and 46, respectively, towhich ex.

trnalconnections may be made as by soldering.

which about the post plane of .disc 54, and

The particular construction of the terminal pieces 38, 39 and 40fis immaterial to the present invention, and hence neednot be described Vat length herein. Y Y o Internally of the cup-shaped base 30, the s`11r` face of bottom 3| is provided with a substantially.

annular groove 41, which extends approximately concentrically. about thepost 34 from terminal piece 39 to terminal piece 4l). In the groove 41 isA positioned a coiled electrical resistance heater wire 48. One 'end of the'heater wire 48 is electrically connected to terminal'piece 39, while the other end is electrically connected-to terminal piece 4U.

The internal wall of the cylindrical portion.,

32 of the base 30 is provided with diametrically 'duced diameter portion Y tively long sleeve 64, the outer end of which is outwardly flanged as indicated at' numeral 65. Preferably the sleevel 64 On each side of each ear 58 is a projection 59 in the groove .of collar 53,' relative tothe post. 34

type of a watch spring, the inner end 6| of which is .polygonally formed in order to embrace the periphery of polygonal Vcollar 55. The outer end 62 of spring 60 isl turned into substantially the at. its extremity is hooked into-a holeY 63 in the purpose. and, reacting centrally on theA polygonal collar (which, it will be recalled, is relatively nonrotatable with respect' to at all times to rotate the disc 54, relative tothe post 31, in .a counterclockwise manner, .considered from the viewpoint represented by Fig. 17. Adjustment of the 'amount of tension in the spring may be made by slipping its polygonal inner end 5| around the polygonalcollar 55; In order to do this, the inner end 6| is momentarily pried away from the surface of collar 55. In normaloperation, however, the Apolygonal portion Ell ofthe spring- 69 effectively anchors it to V the collar-55 in a relatively non-movable manner. Surmounting the polygonal collar 55 on the re `31 of post 34 is is a forced-nt on the post portion 31, so that it does not rotate'relative thereto. Beyond the flange 65, reduced diameter portion 31 is preferably upset an headed over, -as indicated'at numeral 66.

opposite bayonet-type notches 49, extending' The notches 49 have, at one diametrically opposite end of each, relatively deeper portions 50, extending through about, say, 25 of arc, and bottoming on the inner surface of the bottom 3|. The notches 49 also have relatively shallower ldiametrically opposite .portions 5|,"which terminate downwardly as nat ledges or platforms 52. Mounted on .the reduced diameter portion 31 of post 34, on the shoulder afforded byjth'e terf mination of the threaded portion of said post 34,'is a peripherally-grooved collar'53, into the periphery of a perforated thermostatic metal disc 54 of the same general type as the disc 230i The inner face of knob 33 circular depression 61 l stantially to enclose the coil spring BIJ. Extending inwardly from the Y61 is a cylindrical hole is provided with a endeoLwhich is force-fitted a collar or bushing I groove of which relatively loosely ts the internal positions,l a pair of contact buttons 58 and 51,

which are'positioned at suitable radial distances to engage contact plates 4l and 42..when .the

A disc 54 is concave to the right, .as illustrated inv Figures`15 and 11.

Referring now more particularly to Figures 15 vided, at diametrically spaced points and 1'?, it will be seen that the disc 54 is pro'' on its 69 that turns freely on the sleeve 64 on post portion 31. The knob'33 as a whole is thus rotatable relative to the shaft 34, as is the thermostatic disc 54'.

Extending outwardly from the outer periphery of knob 33, at the inner end thereof, are diametrically opposite projections 10. Each projection 1|) includes, in its under surface and at its outer edge, a notch `1| of sufcient width freely t'o receive the upstanding projection 58 on the periphery of thermostatic disc 54. The notches 1| are of suicient depth to accommodate said projections 58 regardless of the direction'of concavity of the disc 54. 'A

The projections 10 extend radially outwardly suillciently'far so thatV they fit only intothe bayonet-type notches 49 in the base member 30. By abutting the ends of Vsaid bayonet notches 49, the said projections 10 limit the rotative move ment of the knob 33 in the base 39. As shown in Fig. 1 4, the outer face or end of the knob 33 is preferably providedwith a posi?- tion-indicating means, such as the arrow 33a. Despite its more complex form, the embodimentof Figuresl4 through 20 operates in substantially the ,same manner as the Fig. 10 embodiment. That is ot say, when the thermostatic in directionfor-each projection of the pair on either side of each ear 58. The disc54, it will be understood, rotates freely' umeral 69 indicates a coil spring, of general e disc 54 provided-for that Coil spring llill is normally -in tension',

the post 31), it tends a relaof sulcient depth subcenter of the depression.

88, into the emergent the ledges l ledges manual -actuation of the knob 33.

` seen that the switch is capable of manual disconnecting operation as well as automatic discon- A 2,327,336 `disc v54 is below a certain temperature, it is concaveto the right, in Fig. 15, and it provides presfrom rotating under the inuence of coil spring 60. When, however, the temperature of the disc 54 increases sufficiently in amount,'said disc snaps` ormoves to a position of opposite concavity, i; e., concave to the left in Fig. 15, and in so doing it lifts the contacts 56 and 51 from the contacts 4| and 42. There is then no frictional deterrent to the rotative inuence of the spring 50, and consequently the thermostatic disc 54 rotates on the post 31 in a counterclockwise manner, to the position shown in Fig. 19. When the disc 54 rotates, it carries with it the knob 33, by engagement of the upstanding projections -58 with the notches 1|. interfere with. this rotative movement, because when thedisc 54 is concave to the left in Fig. 15, said projections 59 are raised above the level of 52 bottomingthe notch portions 5| in base 30.

Assuming now that 'the disc 54 cools while in its Fig. 19 position, it will snap back to its original position of concavity, i. e., concave to the right in Fig. 15. However, under normal conditions there is no automatic tendency for the disc to rotate back to its Fig. 17 position, so it does not A do so, but remains in its Fig. 19 angular position.

The projections 59 thus come to rest upon the 52, as shown in Fig. 20. The movable contacts 55 and 51 are now held out of engagement with the xed contacts 4| and 42 both by reason of the angular displacement of disc 54 and base 30, and by reason of the fact that the engagement of projections 59 with ledges 52 mechanically prevents the disc 54 from overcentering all of the' way to its position of right-hand c oncavity. V

After the disc 54 has thus assumed the Fig. 20 position,`it is necessary manually to rotate the knob.33 in a clockwise manner to reestablish circuit connections. By such rotation, the disc 54 is rotated inra clockwise manner through the engagement of projections 58 with notches 1|, and as the projections 59 pass oifthe ledges 52, said projections sink into the deeper notch portions 50, and bring the relatively movable contacts 56 and 51 back into juxtaposition with the relatively xed contacts 4| and 42. The 'positioning'of the projections 59 in the deeper notch portions 50 provides an additional securing means against counter'clccwise rotation of the disc 54. under the Ainfluence of the coil spring 50, unless said disc 54 is snappedover to its4 position of leftward concavity.

lIt will thus 'be seen that the switch as delscribed is fully capable of automatic circuitbreaking operations, but'capable only of manual A circuit-making operation once itv has been opened.

vThe construction is such, however, 'that the switch may be manuallyopened at any time.

" This is because the sloping character of the pro- `jections 59 makes it possible manually torotate theknob 33,r and with it the disc 54, in a.

motor, for example, with the additional feature of automatic overload protection in its automatic disconnecting capabilities.

By adjusting the threaded portion of post 34 in base 33 an adjustment of the operating, or

Y snapping temperature of disc 54 is brought about.

The projections 59 do not The reasons for such action are described at length elsewhere, and need not be repeated herein. Lock nut 36 secures such Yadjustment once it'is made.

' Figures 2l through 24 represent exemplary circuits in which the switch-of 'the present invention, such as the Fig. 1% embodiment, may be connected i'cr motor protection service.

.The switch is connected by means of contact terminals and 4i! in series with the motor, such as motor 12 in Fig. 21, or other device it is desiredto protect, in series with the source of power, represented in Iig, 2l by power lines 13 and 14, Assuming that knob 33 has been rotated until contacts 56 and 4|, and 51 and 42 respectively make contact., as in Figures 15 and 17, current will flow from one of the power wires 13 to terminal 38, to Contact 4I, to contact 56, through disc 54 to contact 5-1, to Contact 42, through heater. wire 43, 'to contact 43, to terminal 40, to the motor 12 and thence to the other power wire 74. rThus, while the motor is running under its normal conditions, heater wire 48 is subjectv .to electrical current passing through it and because of the heating eect of the current passing through it will be raised in temperature an amount determined by the characteristics of the heater and the vamount of current. The current is also passing through disc 54 and because of this current passage and the inherent electrical resistance oi' disc 54, disc 54 will undergo some temperature rise itself. However, under the normal, safe current values encountered in the circuit, the resulting temperatures are not sufcient to cause disc 54 to snap and thus to break the circuit. However, if excess currents should arise in the circuit, heater 48 will become hot enough (considering the action of the increased current in disc 54 u pon said disc itself) to raise thetemperature of disc 54 to cause it to snap snaps back itdoes so in position to drop contacts counterclockwise manner from the Fig. 17 to the Fig. 19 position. The, sloping faces of these projections 59,-ride up on the ledges 52 under such It is thus necting operation. It may accordingly be used as a; simple on and off switch for an electric 56 and 51 down .angularly displaced from con-y tacts 4| and 42 (Fig. 19). To reset and thus reconnect the circuit, all that is now necessary is to rotate knob 33 in the opposite direction back to its Fig. 16 position, thus causing contacts 5B and 51 to come back into juxtaposition with contacts 4| and 42 in the manner heretofore described. In this Fig. 16 position the contact pressure between contacts 4| and .56, and between contacts 42 and 51, is sufficient to hold the disc 54 from rotating under the'iniluence'of spring 60. circuit is readyto break again at. which time pressure is relieved because of the upward action of the disc 54 away from contacts and 42, and thus the knob 33 and disc 54rotate again.

Figures 22, 23 and 24show other motor protective circuits utilizing the switch embodiment just motor-121s shown as one described., For example, in Figures 22 and 23 the having two windings 15 and 16, it thus being-.o the type-referred to This position is now maintained until the as a dual voltage motor. The windings 15 and 16 may be connected in series (Fig. 23) for high-voltage operation, or in parallel (Fig. 22)

for relatively lower voltage operation, In essence, the elements of the Fig. 23 circuit are the vsame as those of the Fig. 21 circuit, the differcircuit is the same as that of the Fig. 21-circuit, and hence no added description thereof is needed at this point.

'In Fig. 22, however, the connections are somewhat different. One lead of each winding 15 and 16 is-connected to power line 14. The other lead of winding 15 is connected to terminal 39, while the other lead of winding 16 is connected to termina14ll. Terminal 38 is connected to the second power line 13.' Thus the heater. 48 is in series with only 16while the disc 54 is in series with both windings 15 and 16. This disc 54, be-

cause of its electrical resistivity, is .thus its own heater for current passing through either winding 15 or 16, and consequentlythus protects both windings. Winding 16 is additionally protected, however, by the heat accelerating effect of heater 48 on discY 54. -Thus windingv 16 is afforded extra protection.

Fig. 24.shows the use of the switch described in a circuit similar to that of Fig. 21 for the protection'of a motor ,of the type having separate starting and runningA windings 11 and 18. respectively. Starting winding 11 is connected in series with heater 48 and disc 54, like winding 16 of the Fig, 22 circuit, while running'winding 18,

like winding 15 ofi Fig.'22, is connected in series 6 Aasa'miae `ence being in this instance that the two windings are both protected. The operation of the Fig. 23

trols.

28 embodiment it is impossible manually to turn oi the switch once it is turned on (such turning 0E being solely automatic), while it is impossible automatically to turn on the switch once it has been turned oi (such turning on'being accomplished solely manually). In prior embodiments the switch can be turned on or ofi, manually, at any time. Switches of the present type are of use in connection with certain types of circuit con- Referring to Figures 28 and 29, it will be seen that'the peripherally relatively short notches 1I 'knob 33.

in the projections 10 on knob v33 are replaced by notches 8l that extend a relatively much longer peripheral .distance around the under face of In fact, the angular extent of the notches 8l lis preferably only slightly less than y the angular extent of the bayonet-like notches with Only the disc.54. Starting Winding 16 is thus aiorded additional protection.

- Many further variations of structure are pos' sible without departing from the scope of the invention. One of such variations, particular1y with vrespect to the type of thermostatic element utilized, is illustrated in Figures 25, 26, and 27, to which attention is now directed. Referring to these iigures, it will be seen that the thermostatic disc 54 of the Fig. 14 embodiment has been replaced by a rectangular shaped thermostatic plate 19.which'is shown as having arcuate ends, al-

Vtho'ughsuch shape is not important. The plate 19, made of composite thermostatic material such as bimetal, conforms generally to the disclosure of John A. Spencer Patent 1,639,708,

dated August 23, 1927, in that it'is provided in its central portion with a dent or dished region v80 (exaggerated i'n extent in Fig. 27 for clarity).

The customary contact buttons 58 and 51 are carriedbythe plate 19 outside the connes of this dented region 80, anda hole 63 is provided for receiving the end of coil' spring B0. The ears 58 vand -projectionsf59are provided as in the Fig. 14

embodiment. Because lof the mechanical struc- .ture of dented region 89, the plate 19' as a'whole is snap-acting in response' to its ambient temperaturechanges, Vthe` snap movement taking 49 in space 30. By this simple expedient the desired action of the switch is brought about. It will clearly be seen that, with the Fig. 28 ernbodiment, and the switch in circuit making position, if the knob 33 is --rotated in a counterclockwise manner (the same movement thatin the'Fig. 14 embodiment manually disconnected the switch) the disc 54 will not change in angular position, becausethe projections 58 will slide freely in the elongated notches 8i until the pro- .jections 19 on knob 33 abut the ends of bayonetlike notches 49,

However, when said switch has assumed its automatically disconnected position, andthe disc is rotated to the full extent in a counterclockwise position, as illustrated in Fig. 29, it may be manually brought rback to connecting position in the manner heretofore described, because in this tween this Fig. 3o embodiment and the mst embodiment will now be described.

'Valve .82 has a tubular body 83 providing a cylindrical passage 84 terminating as conduitreceiving'jsockets 85. Extending across and 'Y blocking the passage 84 is a tapered plug i cock 85 having an opening 81 therethrough which permits or prevents -ow through the valve dcpending upon the rotative position of plug 86. Plug 86 is held firmly seated by a compression spring 88 reacting at one end against the Wider end' of plug- 86, and at the other end against the inside of aplug 89 threaded in a lateral-exten- 'sion 98 of valveY body 83,

The opposite or narrower end of plug 86 'extends into a lateral extension 9i on the opposite place-in each'direction between the full' and vdotted line positions in Fig. 27.

The Fig. 25 embodiment as a whole operates in the same manner as the Fig. -14 embodiment.-

It will clearly be seen thermally responsive side of valve body 83, and terminates as a polygonal (such as a square) socket'92. Extension 9| terminates as a iiange 93 which is secured as elements of any shape (such as diamond-shaped,

elliptical, square, or' the like) may similarlybe used without departing from the scope of the invention.'

Figures 28 and 29 illustrate an embodiment of the invention that operates somewhat dillereut-` ly'than the previous embodiments'. In this Fig.

by screws 94 to the under side of base 30.

The construction of the control portion of this embodiment is quite similar to that of the Fig. 14 embodiment, except for the construction asso-f.

elated withV the.A central mountingpost or screw 34 of the Fig. 14 embodiment. The latterV is replaced, in Fig. 30, by an unthreaded shaft 95 rotatably received in a bushing 96 threaded into basenSll. Collars 91, and 98 xed on shaft 95 ing 96 in Abase 4.

'terminal piece 40 and spring A|50.

prevent its relative axial movement with respect to bushing 95. A lock nut 99-secures bushing 96 in its adjusted position.. The lower end |00 of shaft 95 is made polygonal in cross section to t slidably in polygonal socket 92 extending from valve plug 86. Y

The bushing 96 has an unthreaded portion |0| of reduced diameter Vat its upper or innerl end,

on'which are mounted grooved disc-mounting collar 53 andhexagonal collar 55. As in the Fig. 14 embodiment, the hexagonal collar 55 is a'forcedlit on portion so that it is non-rotatable relative thereto.

Knob 33 is., in this embodiment, mounted directly on shaft 95, and is made non-rotatable relative thereto as by a set screw |02.

This Fig. 30 embodiment constitutes in effect -a motorized, or relay-operated valve, and operates in the following manner: Through the terminals 38 and 40 an outside source of power is provided for the heater 48.. By also using terminal 39 as in the Fig. 14 embodiment, the device additionally functions as 'a switch to interrupt its own source of power.

Shaft 95, itv will be seen, now operates to rotate in bushing 95 coextensively with the rotations of disc 54 and knob 33, by reason of the projections 58, notches 1|, and set-screw |02. And, through the engagement of polygonal extension |00 with polygonal socket 92, the rotation of shaft; 85 causes coextensive rotation of plug ylili to alter the condition of the valve 82- (from (parts 92 and |00) axialmovement of adjustment. f It will be seen that the other embodiments heretofore described (such as those of Figures 25 and 28) may similarly be applied to a valve structure for operation thereof in the general manner of Fig. 30.

If a simple, non-thermally-responsive manually operative electrical switch i's desired, the Fig. 14

xed contacts 4| and 42 to complete (or make)A connections between'terminals 38 and 39. In the other 4position movable contacts 56 and 51 are angularlydisplaced from fixed contacts 4| and i 42 to disconnect (or break) connections'between terminals38 and 39. The spring disc |03 never snaps to opposite curvature, but its inherent resiliency makes for firm contact pressure when the switch is closed, and positive separation when the switch is open. Because disc |03 never snaps to opposite curvature, spring 60 is unnecessary and has been omitted.

Fig. 32 shows how, by a simple expedient, the Fig. 1`4 switch may be converted into a manually controllable flasher switch, for example. The only change as between Figures 17 and 32 is that the coil spring 60 has been inverted so that it' now-tends to move'the disc 54 clockwise instead of counterclockwise. In other wordspspring 60 now disposes the disc to contact-making position.

-With such a structure, the disc 54, upon heating above itsv predetermined value, snaps to a position of opposite concavity, thereby breaking connections, but without any angular re-positioning of the disc. When the disc 54 then cools, it returns to its initial direction of concavity and thereby re-establishes circuit connections. In the 1 respect that the switch thus'automaticallycloses structure may be modified to that shown in Fig.

r31. Referring to this gure, it will `be seen thatthe bimetallic snap-acting thermostatic disc 54 of the Fig. 14 embodiment described has been replaced by a concave, monometallic spring' disc 03, mounted in the same manner with respect to base 30 and post 34, and carrying movable1 contacts 56 and 51 as heretofore'.

This embodiment has been modiedwith respect to the Fig. 14 embodiment by the elimination of the following elements, which are no longer necessary: heating element 48` and its groove 41, Collar 55, no' longer necessarily polygonal in shape, has been reduced' in size, and 'thecircular indentation 51 in knob 33 has-been eliminated.-

The switch is otherwise firstv embodiment described.

This switchv operates as a simple electrical the same as in the make-and-break switch by'manually rotating the 1 knob 33 with its projections 10 consequently moving to and fro in bayonet-type slots 49. In one` position movable contacts 56 and `51 rest 'on as well as opens, it ments.`

The knob 33 is now manipulated merely to .turn the switch on and off independently of its thermostati'c'activity, the Fig, 32 embodiment in this respect being similar to the Fig. 3l embodiment. A switch of this Fig. 32 type is useful, for example, in an automobilel as a direction signal controller switch. The knob 33 is then used to turn the switch on and off. When manually on; if the heating value of the heater'48 is properly proportioned, the switch will repeatedly,'auto differs from previous embodimatically turn on and off, thus providing for the flashing type-of signal currently in favor.

The spring 60 is not absolutely necessary to the Fig. 32 embodiment, butv it, tends to maintain more certainly the proper angular disposition of the disc, so-that when. the disc automatically closes, it will clearly and directly bring movable contacts 56 and 5l into proper juxtaposition with .xed contacts 4| and 42.

In View ofthe above, it will be seen that-the several objects of the invention are achieved and .other advantageous results attained.

-As many changes could be made in 'carrying 'out the above constructions without departing from the scope of the invention, it is intended that all matter'contained in the above description or 4shown in the accompanying drawings shall'be interpreted as illustrative and not in a limiting sense.

Attention is directed to my copending applications Serial No.' 471,140, filed January 2, 1943,

^ -cally in one plane of ing said flied contact, when .one of its temperature-determined positions, with and serian No. 471-,141,n1ed January 2,1943.' I claim: LA thermostatic control comprising an element the position `of which changes automatimovement in responseto temperature changes, means pivotally mounting, said element to rotate in another plane of movement, meansdisposing said .element to move in one direction in said second plane. of movement, a relatively fixed contact, and a relatively movable contact carried by said element and engagsaid element is insufficient .pressure to resist said disposing means.

2. A thermostatic control comprising a thermostatic material plate, means pivotally mounting said plate to rotate substantially in its own plane, means disposing said plate to rotate in one direction on said mounting, and means carried by said plate and engaging further means to resist the rotating means as long as said plate is in one of its temperature-determined positions.

3. `A thermostatic control comprising a thermostatic material plateymeans pivotally mounting said plate to rotate substantially'in its own plane, spring means disposing saidplate to rotate in 'one direction on said mounting, and means carried by said plate and frictionally engaging further means to resist the spring-means as'long as said plate is in one of its temperature-determined positions.

4. A thermostaticcontrol comprising a thermostatic material plate,means pivotally mounting said plate, means disposing said plate to rotate in one direction cn said mounting, and means carried by said plate and frictionally engaging further means to resist the rotating means as long as said plate is in one of its temperaturedetermined positions, said last-named means beingineffective to resist said rotating means whensaid plate moves to another temperature-determined position.

5. A thermostaticcontrol comprising a thermostatic material plate, means pivotally mountingr said plate, means disposing said plate 'to rotate in one direction on said mounting, a relatively fixed contact, anda relatively movable contact carried by said plate and engaging said fixed contactjwhen-said plate is in one of its temperature-determined positions, with su'fcient 4pressure to resist said` rotating means.

6. A control as set forth in claim 5 in which the two contacts are provided with non-planarl relative to said base,` and control-effecting ele- V ments determined as to condition by the relative rotative positioning -of said plate on said base.

8. A control device comprising a base, a resilient plate mounted substantially parallel to said base and rotatable with respect thereto betweentwo limiting angular positions on an axis perpendicular to the base, at least one projectirig member carried by said plate and forced by the resilience thereof into frictional engagement with sai'd base, means for manually rotating said plate relative to said base, means limiting the movement of said last-named means to determine the said limiting positions, and controlmeans normally urging said plate to move to one of its limiting posi-tions.

10. A control device as set forth in I in which the plate comprises a dished composite thermostatic material element whichV is adapted to snap between two positions of opposite concavity in response to ambient temperature changes, in one of which positions only does it force the projecting member. carried thereby resiliently against said base.

l1. A control devicevas set forth in clam.9, in which the plate comprises a dished composite thermostatic material element which is adapted to snap between two positions of opposite coneffecting elements determined as to'condition by the relative angular positioning of said plate on said base.. 9. A control device comprising a base, a resilient thermostatic lmaterial plate mounted substantially parallel to said base and rotatable with 'respect thereto between two limiting angular positions on an axis perpendicular to the base, atleast one. projecting member carried by said plate and forced by the resilience thereof against said ba'se, means for manually rotating said plate relative to said base, control-effecting elements determined as to condition by the relative angular positioning of said plate on said baseand cavity in response to ambient temperature changes, in one of which positions only does it force the projecting member carried thereby resiliently against said base to resist said urging means, the composite thermostatic material plate, whenever it is in its other position' of concavity, being free to'rotate under the influencent said urging means.

12. A control device as set forth in claim 9 in which the control-eiecting elements comprise electrical contact means adapted to make and break' a circuit respectively in accordance with the relative angular positioning of said plate on said base.

13. A control device as set forth in claim 9 in which the control-effecting elements comprise the parts of a valve adapted to control now therethrough in accordance with the relative angular` positioning of said plate lon said base.

14. An electric snap switch comprising a dished resilient member, a base, means mounting said member substantially parallel to said base, atI

tive to said base to angularly displace said movable contact from said fixed contact.

15. A thermally responsive electric snap switch 'comprising a base, a snap-acting composite thermostatic material disc having two positions of opposite concavity, at leastone `movable contact on said disc, and at least one cooperating xed contacten said base, and means for'rotatingsaid disc on its axis to angularly displace said movable contact from said xed contact.

16. A thermostat comprising a base, a snapacting composite thermostatic material d isc having two positions of opposite concavity,- means mounting said disc substantially parallel to said base, vmeans securing said disc against rotation.

on its axis with respect to said base when said disc is `in one of its positions of concavity, and means urging saiddisc to rotate on its axis when said disc is in its other position of concavity.

17. In a control device, a base member, a post mounted thereon; a spring member mounted on said post substantially parallel to said base and resiliently bearing thereagainst and rotatable with respect to said base in a plane substantially parallel to saidbase, said spring having at least one peripheral projection of' cam shape, means extending upwardly from said base and engaging b oth sides of said projection to define one angular position of said spring, said last-named means extending circumferentially in one direction as a ledge on to which said projection rides against the normal tension of said s'pring to .define a sec*-V ond angular position of the spring, and control means determined as to condition by the relative angular disposition of said spring and said base. 18. In a control device, a base member, a post claim 9,

mounted thereon., a spring member mounted on said post substantially parallel to said base and resiliently bearing thereagainst and rotatable with respect to said base in a plane substantially parallel to said base, said spring having at least one peripheral projection of cam shape, means extending upwardly from said base and engaging both sides of said projection to define one anguiar position of said spring, said last-named means extending circumferentially i'n one direction as a ledge on to which said projection rides against the normal tension of said spring to deline a second angular position of the spring, and control means determined as to condition by the relative angular disposition of said spring and said base, manually operable handle means mounted on said post, and means interconnecting said handle means and said spring for coextensive rotary movement.

19. In a control device, a base member, a post mounted thereon, a. spring member mounted on said post substantially parallel to said base and resiliently bearing thereagainst and rotatable with respect to said base in a plane substantially parallel to said base, said spring having at least one peripheral projection of 4cam shape, means extending upwardly from said base and engaging both sides of said projection to define one angular position of said spring, said lastnamed means extending circumferentially in one direction as a ledge on to which said projection rides against the normal tension of said spring to dene a second angular position of the spring, and control means determined as to condition by the relative angular disposition of said spring and said base, manually operable handle means mounted on said post. and means interconnecting said handle means and said spring for coextensive rotary movement, said interconnecting meansincluding an upstanding projection on said spring which .extends into a suitable recess in said handle means.

20. In a control device, a base member, a post mounted thereon, a spring member mounted on said post substantially parallel to said base and resiliently bearing thereagainst and rotatable withrespect to said base in a plane substantially parallel to said base, said spring having at least one peripheral projection of cam shape, means extending upwardly from said base and engaging both sides of said projection to define one angular position of said spring, said last-named means extending circumferentially in one direction as a ledge on to which said projection rides against the normal tension of said spring to define a second angular position of the spring, and control means determined as to condition by the relative angular disposition ofv said spring and said base, manually operable handle means mounted on said post, and means interconnecting said handle means and said spring for coextensive rotary movement, said interconnecting means including an upstanding projection on said spring which extends into a suitable recess in said handle means, said recess being extended in length whereby a lost-motion connection only is had between said handle means and said spring.

21. -A control device as set forth in claim 17, in which the control means comprise electrical contacts, one of which is mounted on said base, and the other of which is mounted in cooperating position on said spring.

22. A control device as set forth in claim 17,

in which the spring member comprises a dished resilient metal disc.

23. A control device as set forth in claim 17, in which the spring member comprises a dished composite thermostatic metal disc.

24. A control device as set forth in claim 17, in which the spring member comprises a dished composite tnermostatic metal disc capable, under changing ambient temperatures, of snapping between positions of opposite concavity, in only one of which positions does it bear against said base.

25. A control device as set forth in claim 17, in which the spring member comprises a dished composite trieimostatic metal disc capable, under changing ambient temperatures, of snapping between positions of opposite concavity, in only one of which positions does it bear against said base, and further spring means normally urging said disc to the aforesaid second angular position.

26. A control device as set forth in claim 17, in which the spring member comprises a dished composite thermostatic metal disc capable, under changing ambient temperatures, of snapping between positions of opposite concavity, in only one of which positions does it bear against said base, and further spring means normaily urging said disc to the aforesaid second angular position.' said further spring means being rendered inertective, however, as long as said disc is in its position bearing against the base by the friction therebetween.

27. A control device as set forth in claim 17, in which the spring member comprises a dished composite thermostatlc metal disc capable, under changing ambient temperatures, of snapping between positions oi' opposite concavity, in only one of which positions does it bear against said base, and further spring means normaily urging said disc to the aforesaid first angular position.

28. A control device as set forth in claim 19, in which the spring member comprises a dished resilient metal disc.

29. A control device as set forth in claim 19,

. in which the spring member comprises a dished composite thermostatic metal disc.

3U. A control device as set forth in claim 19, in which the spring member comprises a dished composite thermostatic metal disc capable, under' changing ambient temperatures, of snapping between positions of opposite concavity, in only one 4of which positions does it bear against said base, and further spring means normally urgingsaid disc to the aforesaid second angular position.

31. A control device as set forth in claim 19, in which the spring member comprises a dished composite thermostatic metal disc capable, under changing ambient temperatures, of snapping between positions of opposite concavity, in only one of which positions does it bear against said base. and further spring means normally urging said disc to the aforesaid second angular position, said further spring means being rendered ineffective, however, as long as said disc is in its position bearing against the base by the friction therebetween.

32. A control device as set forth in claim 19, in which the spring member comprises a dished composite thermostatic metal disc capable, under changing ambient temperatures, of snapping between positions of opposite concavity, in only one of which positions does it bear against said base,

and further spring means normally urging said disc to the aforesaid first angular position.

, ,bottomed by a ledge, a

in which the control means comprise the relatively stationary and movable parts of a valve.

34. In an electric switch, a cup-like base member, a post axially mounted in said base, a knob mounted on said post in the open end of said base and rotatable with respect to said base, said knob having a recess in its inner end facing the base, said base having at least one bayonet-type slot in its inner wall, said slot having a deep portion and a shallow portion, said shallow portion being bottomed by a ledge, a dished resilient metal disc axially mounted on said post between the inner end of said knob and the base, said disc carrying at least one contact member, a cooperating contact member on the inside bottom of said base, said disc having at least one projection of cam shape extending from its periphery into said bayonet-type slot in said base, and a further projection extending into said recess in said knob, said contacts being resiliently juxtaposed by said disc when said cam-shaped projection is in the deeper portion of the bayonet-type slot, whereby, upon suitable manual rotation of said knob, said disc rotates to displace said contacts angularly,

said cam-shaped projection then riding out of,V

the deeper bayonet-type slot position on to the ledge bottoming the shallower slot portion to likewise displace said contacts axially.

35. In an electric switch, a cup-like base member, a post axially mounted in said base, a knob mounted on said post in the open end of said base and rotatable with respect to said base, said knob having a recess in its inner end facing the base, said base having at least one bayonet-type slot in its inner wall, said slot having a deep portion and a shallow portion, said shallow portion being dished composite thermostatic metal discaxially mounted on said post between the inner end of said knob and the base, said'disc having two positions of opposite concavity, between which it snaps in response to ambient temperature changes, said disc carrying at least one contact member, a cooperating contact member on the inside bottom of said base, said disc having at least one projection of cam shape extending from its periphery into said bayonettype slot in said base, and a further projection extending into said recess in said knob, said contacts being resiliently juxtaposed by said disc when said cam-shaped projection is in the deeper portionof theebayonet-type slotand saiddisc is in its position of concavity facing the base, whereby, upon suitable manual rotation of said knob. said disc rotates to displace said contacts angularly, said cam-shaped projection then riding out of the deeper bayonet-type slot portion on to the ledge bottoming the shallower slot portion to likewise displace said contacts axially, said cam projection being raised above the level of said ledge when said disc is in its position of concavity away from the base.

36. In an electric switch, a cup-like base member, a post axially mounted in said base, a knob mounted on said post in the open end of said base and rotatable with respect to said base, said knob having a recess in its inner end facing the base,

said base having at least one bayonet-type slot in its inner wall, said slot having a deep portion and a shallow portion, said shallow portion being bottomed by a ledge, a dished composite thermostatic metal disc axially mounted on said post between the inner end of said knob and the base, said disc having two positions of opposite concavity, between which it snaps in. response to ambient temperature changes, said disc carrying at least one contact member, a cooperating contact member on the inside bottom of said base, said disc having at least one projection of cam shape extending from its periphery into said bayonet-type slot in said base, and a further projection extending into said recess in said knob, said contacts being resiliently juxtaposed by said disc. when said cam-shaped projection is in the deeper portion of the bayonet-type slot and said disc is in its position of concavity facing the base, whereby, upon suitable manual rotation of said knob, said disc rotates to displace said contacts angularly, said cam-shaped projection then riding out of the deeper bayonet-type slot portion on to the ledge bottoming the shallower slot portion to like- Wise displace said contacts axially, said cam projection being raised above the level of said ledge when said disc is in its position of concavity awa',` from the base, and spring means urging the disc to rotate into contact-juxtaposing position.

37. A thermostatic control comprising a thermostatic element that undergoes change of position in response to temperature change, a base, means mounting said element on said base permitting relative freedom of movement therebetween in addition to the movement consequent upon said change of position, said thermostatic element, however,-in one of its positions frictonally engaging said base to resist said additional movement, and extraneous means disposing said element and said base to undergo said additional relative movement to a diierent stable position when said element is in a position other than its said engaging position. Y

38. A thermostatic control comprising a thermostatic element that undergoes change of position in response to temperatureV change, a base, means mounting said element on said base per- Y mitting relative freedom of movement therebetween in addition to themovement consequent upon said change of position, said thermostatic element, however, in one of its positions frictionally engaging said base to resist said additional movement, and extraneous means disposing said element and said base to undergo said additional relative movement to a dierent stable position when said element is in a position other than its said engaging position and control-eflecting means determined as to condition by the relative positions ofv said base and said element.

39. A control element comprising a base, a spring member mounted thereon but movable with respect thereto, said member having at least one position of stability during which said member frictionally engages said base to resist movement with respect thereto and to make a circuit through the engaging portion, extraneous means disposing said member and said base to undergo relative movement to. a different stable position, and controlled means controlled by said relative movement.

40. A control comprising a base, a thermostatic element mounted on said base, manually actuable extraneous means mounted on said base to undergo relative movement with respect thereto to a different stable position, controlled means actuated by said relative movement, said thermostatic element frictionally engaging said extraneous means to cause relative movement thereof upon temperature change beyond a predeter- 

